Multi-mission radar altimeter: concept and performance

Satellite radar altimeters have proven to be a reliable source of data on sea surface elevation to the precision of several centimeters. Conventional instruments are limited to open ocean applications. This paper describes a new approach to radar altimetry that circumvents most of those limitations. The concept exploits unfocused SAR processing in the along-track direction, and monopulse techniques in the cross-track direction. The result is an instrument that is insensitive (to first order) to small angles of surface slope, is not confused by hill tops or other prominent terrain features, and has a sharper flat surface impulse response than conventional radar altimeters. Full Doppler integration and range curvature correction allow more independent looks than TOPEX, for example, while achieving a resolved footprint of about 250 meters, and requiring less radiated power. An instrument including real-rate on-board processing is described, suitable for a small satellite.